Whatever the cause of the residents’ symptoms, it’s worth taking a moment to consider why water utilities monitor for arsenic in drinking water. Arsenic is tasteless and odorless, and occurs naturally in the Earth’s soils, rocks and minerals. It’s also used in industry as a wood preservative, in paints, metals, drugs and for a variety of other purposes. It is lethal in very high doses. You can learn more in the AWWA book Plain Talk about Drinking Water.